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Abstract

Ascidians have powerful capacities for regeneration but the underlying mechanisms are
poorly understood. Here we examine oral siphon regeneration in the solitary ascidian Ciona
intestinalis. Following amputation, the oral siphon rapidly reforms oral pigment organs (OPO)
at its distal margin prior to slower regeneration of proximal siphon parts. The early stages of oral
siphon reformation include cell proliferation and re-growth of the siphon nerves, although the
neural complex (adult brain and associated organs) is not required for regeneration. Young
animals reform OPO more rapidly after amputation than old animals indicating that regeneration
is age dependent. UV irradiation, microcautery, and cultured siphon explant experiments
indicate that OPOs are replaced as independent units based on local differentiation of progenitor
cells within the siphon, rather than by cell migration from a distant source in the body. The
typical pattern of eight OPOs and siphon lobes is restored with fidelity after distal amputation of
the oral siphon, but as many as sixteen OPOs and lobes can be reformed following proximal
amputation near the siphon base. Thus, the pattern of OPO regeneration is determined by cues
positioned along the proximal distal axis of the oral siphon. A model is presented in which
columns of siphon tissue along the proximal-distal axis below pre-existing OPO are responsible
for reproducing the normal OPO pattern during regeneration. This study reveals previously
unknown principles of oral siphon and OPO regeneration that will be important for developing
Ciona as a regeneration model in urochordates, which may be the closest living relatives of
vertebrates.

The regeneration of the oral siphon (OS) and other distal structures in the ascidian Ciona intestinalis occurs by epimorphosis involving the formation of a blastema of proliferating cells. Despite the longstanding use of ...

Tunicates have high capacities for regeneration but the underlying mechanisms and their relationship to life cycle progression are not well understood. Here we investigate the regeneration of distal structures in the ...

Several of the proteins used to form and maintain myelin sheaths in the central nervous system (CNS) and the peripheral nervous system (PNS) are shared among different vertebrate classes. These proteins include one-to-several ...

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